I'm really impressed by the ARP 1047

[Don Tillman]

I've been researching some VCFs lately, and I'm blown away by how cool
the ARP 1047 Multimode Filter/Resonator is.  

This is a module for the ARP 2500, a standard two pole biquad voltage
controlled filter, but  with a number of extra nice features.  Such
as: 

  The Q is voltage controllable.

  Switchable between unity gain in the passband and unity gain at peak
  resonance.

  It has a notch output and there's a balance control to tune the
  notch zero frequency with respect to the filter tuned frequency.
  
  There's a keyboard percussion mode with keyboard trigger and gate
  inputs, and a separate Q for key up and key down.

And they pack all this in a tiny space.

Unfortunately I've never had a chance to hear or use one.  Does
anybody here have any experience with it?

You can find a very good description of it in the ARP 2500 Owners
Manual downloadable from Anders' site:
  http://omega.tellus.vallentuna.se/anders/
(Look under "sundries".)

There's also a great article by its inventor Dennis Colin, "The
Electrical Design and Musical Applications of an Unconditionally
Stable Combination Voltage Controlled Highpass, Bandpass, Lowpass,
Band Reject Filter/Resonator", Journal of the Audio Engineering
Society Volume 19, Number 11, December 1971 and also available as
Preprint 786, 40th Audio Engineering Society Convention, April 27-30
1971.

  -- Don

-- 
Don Tillman
Palo Alto, California, USA
don at till.com
http://www.till.com